The constitutionality of an act of Congress is a matter always requiring the most careful consideration. The presumptions are in favor of constitutionality, and before a court is justified in holding that the legislative power has been exercised beyond the limits granted, or in conflict with restrictions imposed by the fundamental law, the excess or conflict should be clear. And yet, when clear, if written constitutions are to be regarded as of value, the duty of the court is plain to uphold the Constitution, although in so doing the legislative enactment falls. The reasoning in support of this was in the early history of this court forcibly declared by Chief Justice Marshall in Marbury v. Madison, 1 Cranch, 137, 177, and nothing can be said to add to the strength of his reasoning. His language is worthy of quotation:
 "The Constitution is either a superior paramount law, unchangeable by ordinary means, or it is on a level with ordinary legislative acts, and, like other acts, is alterable when the legislature shall please to alter it.
 "If the former part of the alternative be true, then a legislative act contrary to the Constitution is not law; if the latter part be true, then written constitutions are absurd attempts, on the part of the people, to limit a power in its own nature illimitable.
 "Certainly all those who have framed written constitutions contemplate them as forming the fundamental and paramount law of the nation, and, consequently, the theory of every such government must be that an act
of the legislature repugnant to the Constitution is void.
 "This theory is essentially attached to a written constitution and is consequently to be considered, by this court, as one of the fundamental principles of our society.
 "It is emphatically the province and duty of the judicial department to say what the law is. Those who apply the rule to particular cases must of necessity expound and interpret that rule. If two laws conflict with each other, the courts must decide on the operation of each.
 "So if a law be in opposition to the Constitution; if both the law and the Constitution apply to a particular case, so that the court must either decide that case conformably to the law, disregarding the Constitution, or conformably to the Constitution, disregarding the law, the court must determine which of these conflicting rules governs the case. This is of the very essence of judicial duty.
 "If, then, the courts are to regard the Constitution, and the Constitution is superior to any ordinary act of the legislature, the Constitution, and not such ordinary act, must govern the case to which they both apply.
 "The particular phraseology of the Constitution of the United States confirms and strengthens the principle, supposed to be essential to all written constitutions, that a law repugnant to the Constitution is void; and that courts as well as other departments are bound by that instrument."
 This judicial duty of upholding the provisions of the Constitution as against any legislation conflicting therewith has become now an accepted fact in the judicial life of this nation. That in the enforcement of this rule the decisions, national and State, are not all in harmony is not strange. Conflicts between constitutions and statutes have been easily found by some courts. Fairbank v. United States.,
<http://www.versuslaw.com>¶ 11-20; 181 U.S. 283 (1901).
It would be a strange rule of construction that language granting powers is to be liberally construed and that language of restriction is to be narrowly and technically construed. Especially is this true when in respect to grants of powers there is as heretofore noticed the help found in the last clause of the eighth section, and no such helping clause in respect to prohibitions and limitations. The true spirit of constitutional interpretation in both directions is to give full, liberal construction to the language, aiming ever to show fidelity to the spirit and purpose. Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 26; 181 U.S. 283 (1901).
We know historically that it was one of the compromises which entered into and made possible the adoption of the Constitution. It is a restriction on the power of Congress; and as in accordance with the rules heretofore
noticed the grants of powers should be so construed as to give full efficacy to those powers and enable Congress to use such means as it deems necessary to carry them into effect, so in like manner a restriction should be enforced in accordance with its letter and spirit, and no legislation can be tolerated which, although it may not conflict with the letter, destroys the spirit and purpose of the restriction imposed. If, for instance, Congress may place a stamp duty of ten cents on bills of lading on goods to be exported it is because it has power to do so, and if it has power to impose this amount of stamp duty it has like power to impose any sum in the way of stamp duty which it sees fit. And it needs but a moment's reflection to show that thereby it can as effectually place a burden upon exports as though it placed a tax directly upon the articles exported. It can, for the purposes of revenue, receive just as much as though it placed a duty directly upon the articles, and it can just as fully restrict the free exportation which was one of the purposes of the Constitution.
 The power to tax is the power to destroy. And that power can be exercised not only by a tax directly on articles exported, but also and equally by a stamp duty on bills of lading evidencing the export. To the suggestion that a stamp duty is necessarily small in amount, we reply that the fact is to the contrary. The act by which the stamp tax in question was imposed imposes a like tax on many other instruments, and in some instances graduating the amount thereof by the value of the property conveyed or affected by the instrument taxed. Thus, "each sale, agreement of sale, or agreement to sell any products or merchandise at any exchange, or board of trade, or other similar place" is subject to a stamp tax in the sum of one cent for each hundred dollars of value of the property sold or agreed to be sold. Bills of exchange are likewise taxed by a graduated scale. Deeds or other instruments for the conveyance of land are charged with a stamp tax of fifty cents for each five hundred dollars of value of property conveyed. And so of others. It is a well-known fact that under this graduated system many instruments are subject to stamp duties of large amount. No question has ever been raised as to this power of graduating, and if valid in the cases of bills of exchange, agreements of sale, or conveyances of property, it is equally valid as to bills of lading. The fact that Congress has not graduated the stamp tax on bills of lading does not affect the question of power. By a graduated system, although the tax is called a tax on "the vellum, parchment or paper" upon which transactions are written, or by which they are evidenced, a burden may be cast upon exports sufficient to check or retard them, and which will directly conflict with the constitutional provision that no tax or duty shall be laid thereon. The question of power is not to be determined by the amount of the burden attempted to be cast.
The constitutional language is "no tax or duty." A ten cent tax or duty is in conflict with that provision as certainly as an hundred dollar tax or duty. Constitutional mandates are imperative. The question is never one of amount but one of power. The applicable maxim is "obsta principiis," (Resist the first advances.) not "de minimis non curatur lex." (the law does not concern itself with trifles.) Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 28-9; 181 U.S. 283 (1901).
But surely under this limitation Congress can impose an export tax neither on one article of export, nor on all articles of export. In other words, the purpose of the restriction is that exportation, all exportation, shall be free from national burden. This intent, although obvious from the language of the clause itself, is reinforced by the fact that in the constitutional convention Mr. Clymer moved to insert after the word "duty" the words "for
the purpose of revenue" but the motion was voted down. So it is clear that the framers of the Constitution intended not merely that exports should not be made a source of revenue to the National Government, but that the National Government should put nothing in the way of burden upon such exports. If all exports must be free from national tax or duty, such freedom requires not simply an omission of a tax upon the article exported, but also a freedom from any tax which directly burdens the exportation, and, as we have shown, a stamp tax on a bill of lading, which evidences the export is just as clearly a burden on the exportation as a direct tax on the article mentioned in the bill of lading as the subject of the export. Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 32; 181 U.S. 283 (1901).
The merchant could not send an agent with every vessel, to inform the consignee of the cargo what articles he had shipped, and prove the contract of the master if he failed to deliver them in safety. A bill of lading, therefore, or some equivalent instrument of writing, is invariably associated with every cargo of merchandise exported to a foreign country, and consequently a duty upon that is, in substance and effect, a duty on the article exported." Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 39; 181 U.S. 283 (1901).
In other words, that decision affirms the great principle that what cannot be done directly because of constitutional restriction cannot be accomplished indirectly by legislation which accomplishes the same result.
Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 40; 181 U.S. 283 (1901).
In the Income Tax Cases, Pollock v. Farmers' Loan & Trust Co., 157 U.S. 429; 158 U.S. 601, the constitutional provision as to the apportionment of direct taxes was elaborately considered, and it was held that a tax on the income made up of the rents of real estate and one on the income from personal property were substantially direct taxes on the real estate and the personalty. In the first of these cases, on page 581, discussing the principles of constitutional construction, the Chief Justice said:  "If it be true that by varying the form the substance may be changed, it is not easy to see that anything would remain of the limitations of the Constitution or of the rule of taxation and representation, so carefully recognized and guarded in favor of the citizens of each State. But constitutional provisions cannot be thus evaded. It is the substance and not the form which controls, as has indeed been established by repeated decisions of this court. Thus in Brown v. Maryland, 12 Wheat. 419, 444, it was held that the tax on the occupation of an importer was the same as a tax on imports, and therefore void. And Chief Justice Marshall said: 'It is impossible to conceal from ourselves that this is varying the form without varying the substance. It is treating a prohibition which is general, as if it were confined to a particular mode of doing the forbidden thing. All must perceive, that a tax on the sale of an article, imported only for sale, is a tax on the article itself.'
 "In Weston v. Charleston, 2 Pet. 449, it was held that a tax on the income of United States securities was a tax on the securities themselves, and equally inadmissible. The ordinance of the city of Charleston involved in that case was exceedingly obscure; but the opinions of Mr. Justice Thompson and Mr. Justice Johnson, who dissented, make it clear that the levy was upon the interest of the bonds and not upon the bonds, and they held that it was an income tax, and as such sustainable; but the majority of the court, Chief Justice Marshall delivering the opinion, overruled that contention.
 "So in Dobbins v. Commissioners, 16 Pet. 435, it was decided that the income from an official position could not be taxed if the office itself was exempt.
 "In Almy v. California, 24 How. 169, it was held that a duty on a bill of lading was the same thing as a duty on the article which it represented; in Railroad Co. v. Jackson, 7 Wall. 262, that a tax upon the interest payable on bonds was a tax not upon the debtor, but upon the security; and in Cook v. Pennsylvania, 97 U.S. 566, that a tax upon the amount of sales of goods made by an auctioneer was a tax upon the goods sold. Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 44-48; 181 U.S. 283 (1901).
'The substance, and not the shadow, determines the validity of the exercise of the power.' Postal Telegraph Co. v. Adams, 155 U.S. 688, 698." Fairbank v. United States., 1901.SCT.40110 <http://www.versuslaw.com>¶ 49; 181 U.S. 283 (1901).